Brian Hook, head of the department's Iran Action Group, said that he emailed the Master about sailing it to an area where the US could seize it.
In addition, the US Department of Justice, which had tried to block the vessel’s release from detention off Gibraltar, also issued a warrant to seize the tanker.
The US blacklisted the tanker late last week, as a US Treasury Department statement claimed the vessel was being used to transport 2.1 mill barrels of Iranian crude oil for the benefit of Iran's Revolutionary Guard, which the US had designated a terrorist organisation.
Capt Kumar ignored the emails and as a result, the US imposed sanctions on him personally when the VLCC was blacklisted.
On Twitter, Iran's foreign minister Javad Zarif accused the US of "outright bribery".
On Friday of last week, the US Treasury had designated the VLCC as a ‘blocked property’ using anti-terrorism rules drawn up after the 9/11 attacks. Also blacklisted was the vessel's Master, using measures targeting ‘those providing support to terrorism or acts of terrorism.’ The US State Department did not name any other crew members.
“Vessels like the ‘Adrian Darya 1’ enable the IRGC-QF to ship and transfer large volumes of oil, which they attempt to mask and sell illicitly to fund the regime’s malign activities and propagate terrorism,” claimed Sigal Mandelker, the US Treasury's under-secretary for terrorism. “Anyone providing support to the ‘Adrian Darya 1’ risks being sanctioned. The path to relief is to change course and not allow the IRGC-QF to profit from illicit oil sales.”
As a result, US persons are now prohibited from conducting business with either the VLCC or with Capt Kumar. US entities are also required to implement a freeze on any property or assets associated with the vessel or her Master.
The US authorities believed that the vessel was still bound for Syria. "We have reliable information that the tanker is underway and headed to Tartous, Syria. I hope it changes course. It was a big mistake to trust [Iranian foreign minister Javad] Zarif," Pompeo said.
This week, it was reported that the VLCC has turned its tracking system off.